1. Field of the Disclosure
The invention relates to a fuel oxygen transport reactor that may be used together with a turbine and/or a water tube boiler and a method of operating an oxygen transport reactor to obtain full evaporation of a liquid fuel prior to contact and combustion with an oxygen-enriched atmosphere.
2. Description of the Related Art
The “background” description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description which may not otherwise qualify as prior art at the time of filing, are neither expressly or impliedly admitted as prior art against the present invention.
Fossil fuels are considered to be a main source of energy for the developed and developing world. Fossil fuels produce CO2 which is thought to be a main contributor of global warming (Habib M. A., Nemitallah M. A., Ben-Mansour R., Recent Development in Oxy-Combustion Technology and Its Applications to Gas Turbine Combustors and ITM Reactors, dx.doi.org/10.1021/ef301266j; Energy Fuels 2013, 27, 2-19, incorporated herein by reference). Due to the shortage of natural gas, liquid fuels are presently being heavily used. As well, liquid fuels are byproduct of other process industries and are being used along with natural gas for producing steam and energy.
Liquid fuels produce large amounts of carbon dioxide. In order to capture CO2, different techniques are currently available and include technologies of pre-combustion, post-combustion and oxyfuel combustion. As a promising CCS technology, oxyfuel combustion can be used to existing and new power plants (B. J. P. Buhre, L. K. Elliott, C. D. Sheng, R. P. Gupta, T. F. Wall, Prog. Energy Combust. Sci. 31 (2005) 283-307, incorporated herein by reference). In oxycombustion, a fuel is oxidized in a nearly nitrogen-free, diluted mixture such that the products consist mainly of CO2 and water vapor, enabling a relatively simple and inexpensive condensation separation process (Nemitallah M. A., Habib M. A., Ben Mansour R., Investigations of oxy-fuel combustion and oxygen permeation in an ITM reactor using a two-step oxy-combustion reaction kinetics model, Journal of Membrane Science 2013, 432, 1-12, incorporated herein by reference).
For this process, the required pure oxygen is obtained via cryogenic distillation. This process of separation of O2 is very costly (Sundkvist S, Griffin T, Thorshaug N. AZEP e development of an integrated air separation membrane e gas turbine. In: Second Nordic Mini symposium on Carbon Dioxide Capture and Storage, Goteborg, Sweden, Oct. 26, 2001, pp. 52-57, incorporated herein by reference). The thermodynamic and economic penalties incurred by the use of cryogenic air separation unit could easily offset any advantages gained by oxyfuel combustion. Such short comings have prompted many researchers to investigate the use of alternative air separation systems. One of the alternatives to separation of oxygen from air is the use of Ion Transport Membranes (ITMs) which may reduce the penalty of air separation units in oxycombustion. These ITMs have the capability of separating the oxygen from air at elevated temperature typically above 700° C. Oxygen permeation through these membranes is a function of partial pressure of oxygen across the membranes, membrane thickness and temperature at which these membranes are operating (U. Balachandran, M. S. Kleefisch, T. P. Kobylinski, S. L. Morissette, S. Pei, Oxygen ion-conducting dense ceramic membranes (Assigned to Amoco Co.), U.S. Pat. No. 5,639,437 (1997), incorporated herein by reference). The use of membranes in gas separation processes has been predicted to increase by a factor of five by 2020 (Bernardo P, Drioli E, Golemme G. Membrane gas separation: a review of state of the art. Industrial Chemical Engineering 2009; 48(1):4638-63, incorporated herein by reference), and many studies are currently being conducted to improve the chemical stability and performance under more demanding operational conditions.
Membrane reactor technology is a promising technology and it may be applied for carbon capture by direct combustion of permeated oxygen in the permeate side of the membrane with fuel or this technology can be used for the production of hydrogen from natural gas (Rahimpour M R, Mirvakili A, Paymooni K. A novel water perm-selective membrane dual-type reactor concept for Fischer Tropsch synthesis of GTL (gas to liquid) technology. ENERGY 2011, 36, 1223-1235, incorporated herein by reference). The membrane reactor is a novel technology for the production of hydrogen from natural gas. It may provide hydrogen production, e.g. at refueling stations and has the potential of inexpensive CO2 separation (Sjardin M, Damen K J, Faaij A P. Techno-economic prospects of small-scale membrane reactors in a future hydrogen-fuelled transportation sector. ENERGY 2006, 31, 2523-2555, incorporated herein by reference). In a recent study (Ben-Mansour R., Habib M., Badr H., Uddin A., Nemitallah M. A., Characteristics of Oxy-fuel Combustion in an Oxygen Transport Reactor, Energy Fuels. 2012, dx.doi.org/10.1021/ef300539c Energy Fuels 2012, 26, 4599-4606, incorporated herein by reference), the characteristics of oxyfuel combustion in an oxygen transport reactor (OTR) have been investigated. In this work, cylindrical reactor walls were made of dense, nonporous, mixed-conducting ceramic membranes that only allow oxygen permeation from the outside air into the combustion chamber and the simulations have been done for different composition of CH4/CO2 mixtures and for different mass flow rates. The comparison between reactive and separation-only OTR units showed that combining reaction and separation increases significantly O2 permeation rate to about 2.5 times as compared to the case of separation only. Mancini and Mitsos (Mancini N D, Mitsos A. Ion transport membrane reactors for oxy-combustion part II: analysis and comparison of alternatives. ENERGY, 2011, 36(8):4721, 39, incorporated herein by reference) conducted a comparison between reactive and separation-only ITMs to assess the relative merits and disadvantages of each on an ITM monoliths structure reactor for co-current and counter-current flow configuration. They have developed an oxygen permeation model taking into account the effects of oxy-combustion in the permeate side of the membrane based (Mancini N D, Mitsos A. Ion transport membrane reactors for oxy-combustion e Part I: intermediate fidelity Modeling, ENERGY 2011, 36, 4701-4720, incorporated herein by reference). The results show that although a reactive ITM significantly improves the partial pressure driving force, practical reactor engineering considerations indicate that this concept is not superior to counter-current separation-only ITMs, mainly because of the stringent temperature limitations of the membrane material; however, the temperature limit was acceptable in case of co-current flow.
Akin and Jerry (Akin F T, Jerry, Lin Y S. Oxygen permeation through oxygen ionic or mixed-conducting ceramic membranes with chemical reactions. Journal of Membrane Science, 2004, 231, 133-146, incorporated herein by reference) presented a simple mathematical analysis, coupled with experimental data, on the effects of hydrocarbon flow rate and reactivity with oxygen on the oxygen permeation in an ionic or mixed conducting ceramic membrane reactor for partial oxidation of hydrocarbon. In their work, Oxygen permeating through the BYS membrane reacted with methane or ethane, with main reaction being oxidative coupling of methane (OCM) in the former (Akin F T, Lin Y S. Oxidative coupling of methane in dense ceramic membrane reactor with high yields. AIChE J. 2002, 48, 2298-2306, incorporated herein by reference) and selective oxidation of ethane (SOE) to ethylene for the latter (Akin F T, Lin Y S. Selective oxidation of ethane to ethylene in a dense tubular membrane reactor. J. Membrane Sci. 2002, 209, 457-467, incorporated herein by reference). They showed that for a membrane under reaction conditions with a specific reducing gas, the oxygen permeation flux depends strongly on the oxidation reaction rate and the reducing gas flow rate.
In order to address the deficiencies and drawbacks of conventional oxycombustors the present inventors disclose an oxygen transport reactor for the conversion of liquid fuels into energy while capturing the CO2. The oxygen transport reactor has two functions: CO2 separation and fuel reaction with O2. Cylindrical reactor walls made of dense, nonporous ceramic membranes allow only oxygen permeation from the outside air into the combustion chamber. The liquid fuel is sprayed and evaporated in the permeate side inside a porous pipe. The permeate oxygen burns in a mixture of CO2 and fuel (sweep gas) that enters the reactor resulting in combustion products composed of H2O and CO2. A complete design for a water tube boiler utilizing an oxygen transport reactor is provided.